Rule reminder
An alternative Italian cleft uses: È + [subject] + a + infinitive (instead of che + conjugated verb). Example: È stato Marco a chiamare (= It was Marco who called). This construction is very common in spoken Italian and emphasises the SUBJECT who performed an action. Past: È stato/a/i/e + subject + a + infinitive. Present: È + subject + a + infinitive. Note: 'essere' agrees with the subject in gender and number.
Convert to the 'essere + a + infinitive' cleft: 'Marco ha chiamato per primo.'